The present invention relates to a filtering technique for eliminating noise superimposed on digital data.
Such a moving average process as applied to a rotating device disclosed in a patent document 1 (Japanese Unexamined Patent Publication No. Hei 7(1995)-311082 (description of noise eliminator in particular)) or a process using a digital filter has heretofore been performed in a filter circuit for eliminating noise superimposed on digital data.
In the filter circuit which performs the moving average process, however, when the type of noise is of single noise other than stationary noise, the result of average processing of samplings before and after the occurrence of noise deviates from a value to be outputted originally as the single noise becomes larger. On the other hand, since a filter circuit using a digital filter, e.g., an IIR (Infinite Impulse Response) filter generally needs a multiplier, a register and a cumulative adder, a circuit scale increases. There has thus been a demand for a filter circuit which can remove single noise effectively and is relatively easy in circuit configuration.